Several times now I've seen UFOs fly close to a radar tower and then start buzzing around it like a lost bee. It's like they can sense there's something there, but can't find the base to attack. They fly 100km this way, turn around, fly 100km another way, randomly criss-crossing the area around the radar tower. It seems they get stuck there. Perhaps this is supposed to be by design, but the current implementation looks kind of silly, like it's lost rather than flying a search pattern.

So far I've seen it happen to Harvesters and Corruptors, I'm not sure if it only affects larger UFOs or not.